High Resolution 3D X-ray Diffraction Microscope

提出了一种扩展形式的x射线晶体学对小细胞的三维成像（或相当于开发和使用软x射线衍射显微镜用于细胞生物学）。该仪器设计用于提供分辨率优于20 nm的冷冻水合细胞和亚细胞结构的三维图像。该仪器不使用光学元件来形成图像，而是记录相干照射物体的衍射模式，并使用借鉴晶体学的技术，使用迭代算法进行重建。这样分辨率就不受光学器件的限制，未来的发展应该进一步提高分辨率限制。非晶体样品的衍射图是连续的（散斑）图。与晶体的情况不同，这种模式包含足够的信息，通过在更细的尺度上采样衍射模式来克服晶体学的相位问题。国家同步加速器光源的波动辐射用于提供样品的相干照明。用CCD检测器记录衍射图样。除了需要的信息外，还要特别注意保护探测器不受其他信息的干扰。单个图案产生二维图像。为了获得三维重建，试样被旋转并收集了一组衍射图案。冷冻水化试样用于减少辐射损伤的影响。

The three dimensional imaging of a small cell by an extended form of X-ray crystallography (or equivalently the development and use of a soft X-ray diffraction microscope for use in cell biology) is proposed. This instrument is designed to provide three-dimensional images of frozen hydrated cellular and sub-cellular structures at better than 20 nm resolution. The instrument does not use optical elements to form the image instead it records the diffraction pattern of the coherently illuminated object, and using techniques borrowed from crystallography, performs the reconstruction using an iterative algorithm. This way the resolution is not limited by the optics, and future developments should improve the resolution limit further. The diffraction pattern from a non-crystalline specimen is a continuous (speckle) pattern. Unlike the case with crystals this pattern contains sufficient information to overcome the phase problem of crystallography by sampling the diffraction pattern at a finer scale. Undulator radiation at the National Synchrotron Light Source is used to provide coherent illumination of the specimen. The diffraction pattern is recorded using a CCD detector. Special care is taken to shield the detector from all but the desired information. A single pattern yields a two-dimensional image. To obtain three-dimensional reconstruction the specimen is rotated and a set of diffraction patterns is collected. Frozen hydrated specimens are used to minimize the effects of radiation damage.